System for Blood Separation with Gravity Valve for Controlling a Side-Tapped Separation Chamber

ABSTRACT

A disposable blood separation set and a centrifugal blood processing system comprising a blood processing chamber adapted to be mounted on a rotor of a centrifuge; a frustro-conical cell separation chamber in fluid communication with the processing chamber, the cell separation chamber having an inlet, a primary outlet and a side tap outlet adjacent the inlet. A valve that is responsive to centrifugal force (a “gravity” valve) selects between the outlet and the side tap outlet. The gravity valve is mounted on the rotor. When the rotor spins at high speed, the gravity valve may open the primary outlet and close the side tap outlet. When the rotor spins at a lower speed, the gravity valve may open the side tap outlet and close the primary outlet.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority of U.S. Provisional ApplicationSer. No. 61/496,166, currently pending, filed on Jun. 13, 2011. Thedisclosure of the above-identified application is hereby incorporated byreference in its entirety as if set forth herein in full for all that itteaches and for all purposes.

BACKGROUND OF INVENTION

Blood collection and blood processing play important roles in theworldwide health care system. In conventional large scale bloodcollection, blood is removed from a donor or patient, separated into itsvarious blood components via centrifugation, filtration, or elutriationand stored in sterile containers for future infusion into a patient fortherapeutic use. The separated blood components typically includefractions comprising red blood cells, white blood cells, platelets, andplasma. Separation of blood into its components can be performedcontinuously during collection or can be performed subsequent tocollection in batches, particularly with respect to the processing ofwhole blood samples. Separation of blood into its various componentsunder highly sterile conditions is critical to many therapeuticapplications.

Recently, apheresis blood collection techniques have been adopted inmany large scale blood collection centers wherein a selected componentof blood is collected and the balance of the blood is returned to thedonor during collection. In apheresis, blood is removed from a donor andimmediately separated into its components by on-line blood processingmethods. Typically, on-line blood processing is provided by densitycentrifugation, filtration, or diffusion-based separation techniques.One or more of the separated blood components are collected and storedin sterile containers, while the remaining blood components are directlyre-circulated to the donor. An advantage of this method is that itallows more frequent donation from an individual donor because only aselected blood component is collected and purified. For example, a donorundergoing plateletpheresis, whereby platelets are collected and thenon-platelet blood components are returned to the donor, may donateblood as often as once every fourteen days.

Apheresis blood processing also plays an important role in a largenumber of therapeutic procedures. In these methods, blood is withdrawnfrom a patient undergoing therapy, separated, and a selected fraction iscollected while the remainder is returned to the patient. For example, apatient may undergo leukapheresis prior to radiation therapy, wherebythe white blood cell component of his blood is separated, collected andstored to avoid exposure to radiation.

Both conventional blood collection and apheresis systems typicallyemploy differential centrifugation methods for separating blood into itsvarious blood components. In differential centrifugation, blood iscirculated through a sterile blood processing vessel which is rotated athigh rotational speeds about a central rotation axis. Rotation of theblood processing vessel creates a centrifugal force directed alongrotating axes of separation oriented perpendicular to the centralrotation axis of the centrifuge. The centrifugal force generated uponrotation separates particles suspended in the blood sample into discretefractions having different densities. Specifically, a blood sampleseparates into discrete phases corresponding to a higher densityfraction comprising red blood cells and a lower density fractioncomprising plasma. In addition, an intermediate density fractioncomprising platelets and leukocytes forms an interface layer between thered blood cells and the plasma. Descriptions of blood centrifugationdevices are provided in U.S. Pat. No. 5,653,887 and U.S. Pat. No.7,033,512.

To achieve continuous, high throughput blood separation, extraction orcollect ports are provided in most blood processing vessels. Extractionports are capable of withdrawing material from the separation chamber atadjustable flow rates and, typically, are disposed at selected positionsalong the separation axis corresponding to discrete blood components. Toensure the extracted fluid exiting a selected extraction port issubstantially limited to a single phase, however, the phase boundariesbetween the separated blood components must be positioned along theseparation axis such that an extraction port contacts a single phase.For example, if the fraction containing white blood cells resides tooclose to the extraction port corresponding to platelet enriched plasma,white blood cells may enter the platelet enriched plasma stream exitingthe blood processing vessel, thereby degrading the extent of separationachieved during blood processing. Although conventional blood processingvia density centrifugation is capable of efficient separation ofindividual blood components, the purities of individual componentsobtained using this method is often not optimal for use in manytherapeutic applications.

As a result of the inability to achieve optimal purity levels usingcentrifugation separation alone, a number of complementary separationtechniques based on filtration, elutriation in a cell separation chamberand affinity-based techniques have been developed to achieve the optimalpurities needed for use of blood components as therapeutic agents. Thesetechniques, however, often reduce the overall yield realized is and mayreduce the therapeutic efficacy of the blood components collected.Exemplary methods and devices of blood processing via filtration,elutriation and affinity based methods are described in U.S. Pat. No.6,334,842.

A centrifugal blood component separation apparatus has been described incommonly assigned U.S. Pat. No. 7,605,388, for instance. As described inU.S. Pat. No. 7,605,388, an optical cell may be configured such thatwhite blood cells can be extracted through a first extraction port,plasma and/or platelets can be extracted through second extraction port,and red blood cells can be extracted through third extraction port. Asalso mentioned in U.S. Pat. No. 7,605,388 (but not shown), optical cellsof a blood separation vessel can include one or more dams positionedproximate to the extraction ports to facilitate selective extraction ofseparated blood components having reduced impurities arising fromadjacent components. The use of dams in blood processing via densitycentrifugation is known in the art and described in U.S. Pat. Nos.6,053,856; 6,334,842 and 6,514,189.

SUMMARY OF THE INVENTION

This invention provides methods, devices and device components forimproving the processing of fluids comprising fluid components, such asblood, components of blood and fluids derived from blood. Methods,devices and device components of the present invention are capable ofmonitoring and controlling separation of blood into discrete componentsand subsequent collection of selected components. In particular, it hasbeen found that white blood cells may be extracted from the bottom of afluidized bed leuko-reduction chamber (or cell separation chamber) whileplasma and platelets are removed from the top of the separation chamber.The system and method may enable collection of white blood cells withfewer platelets. An embodiment controls flow selection between the topof the separation chamber and the bottom of the separation chamber by avalve that is responsive to centrifugal force, hereinafter a “gravity”valve. The gravity valve is mounted on a rotor of a centrifugal bloodseparation device. When the rotor spins at high speed, thereby producinga high gravity field, the gravity valve may open a first flow path andmay close a second flow path. When the rotor spins at a lower speed, thegravity valve may open the second flow path and close the first flowpath. The flow paths may comprise tubular lines of flexible polymer. Thegravity valve allows a line to be closed or opened dependant on thespeed of rotation of the rotor without requiring electrical connectionsbetween the generally stationary blood separation device and thespinning rotor. Moreover, cells may be withdrawn from the bottom of theseparation chamber through the second flow path with only a small amountof additional fluid, or “flush volume”, added to the separation chamber.

A function of the centrifuge blood processing system described hereinmay be the collection of white blood cells or other selected bloodcomponents such as mesenchymal stem cells. In a preferred embodiment,certain functions of the centrifugal blood separator are controlled byan optical monitoring system. A cell separation chamber, adapted to bemounted on a rotor of the centrifuge blood processing system, comprisesan inlet for receiving plasma, platelets and white blood cells, or“buffy coat”, an outlet for ejecting plasma and platelets from theseparation chamber, and a side tap outlet for ejecting white blood cellsand plasma from the separation chamber. Red blood cells or plasma may becollected or returned to a donor. White cells or other components suchas mesenchymal stem cells and plasma may be collected for therapeuticpurposes.

According to an embodiment, an optical cell of a circumferential bloodprocessing vessel comprises at least a buffy coat extraction port and ared blood cell extraction port. White cells collect at the buffy coatextraction port. This configuration allows white cell-containing buffycoat to be withdrawn from the blood processing vessel through the buffycoat extraction port for further separation in the fluidized-bedfiltration chamber or cell separation chamber. The cell separationchamber has a generally conical shape, with a buffy coat inlet at theapex of the cone and adapted to be mounted with the buffy coat inletradially outwardly on the centrifuge rotor. A plasma outlet is centrallylocated in the base of the cone and is adapted to be mounted radiallyinwardly on the centrifuge rotor. The base may also have a slightconical shape to conduct platelets and plasma to the plasma outlet. Theinlet may comprise a pipe or tube extending into the interior of theseparation chamber such that a circumferential well is formed betweenthe pipe and an interior conical wall of the separation chamber. A sidetap white blood cell extraction port penetrates the conical wall intothe circumferential well. White blood cells (“WBC”) fall into the welland white blood cells and plasma are withdrawn from the separationchamber through the side tap extraction port for collection.

Features of the disclosed apparatus and method may reduce the loss ofwhite blood cell product or selected cell components such as mesenchymalstem cells that can occur during periodic flushing of white blood cellsthrough the platelet outlet, as in conventional separation chamber.

Further features may provide more continuous steady flow through a cellseparation chamber, thereby providing a greater volume of bloodcomponents processed per unit time. Other features may produce acollected white blood cell (or other selected cell types) product havingfewer platelets than conventional collection methods, and thus improvedpurity.

Yet other features of the disclosed apparatus and method may reducecollection flow rates out of the separation chamber and to reduce thevolume of WBC-containing fluid extracted from the separation chamber. Alow WBC extraction volume may be achieved with a cycled extraction ratethrough the side-tap port that may be triggered by detection of asaturated separation chamber by the optical sensor. Total flow throughthe separation chamber may be kept constant.

A cell separation chamber for cell collection, as disclosed herein, maynot be limited by insufficient available plasma for flushing theselected cells through the platelet outlet, as in conventionalseparation chamber.

For donors whose blood has a high hematocrit, it has sometimes beendifficult or impossible to reduce the RPM of the centrifuge rotor (andthereby reduce the gravitational field of the centrifuge) sufficientlyto allow complete flushing of WBC out of the platelet outlet of aconventional separation chamber. The disclosed apparatus may does notrequire a reduction in the centrifuge gravitational field when whiteblood cells are removed from the separation chamber.

These and other features and advantages will be apparent from thefollowing description, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of one embodiment of an apheresis system,which can be used in or with the present invention.

FIG. 2 illustrates a tubing and bag set including an extracorporealtubing circuit, a cassette assembly, collection bag assembly, a bloodprocessing vessel, and a cell separation chamber for use in or with thesystem of FIG. 1.

FIG. 3 is a perspective view of a blood processing vessel and the cellseparation chamber.

FIG. 4 is a plan view of the cell separation chamber of FIG. 3.

FIG. 5 is a cross-sectional view of the cell separation chamber of FIG.4.

FIG. 6 is a top perspective view of a centrifuge rotor and gravityvalve, showing a separation chamber mounted thereon. First and secondoutflow paths from the separation chamber are also shown.

FIG. 7 is a top plan view of the centrifuge rotor, gravity valve, andthe separation chamber of FIG. 6.

FIG. 8 is a top plan view of the gravity valve of FIG. 6.

FIG. 9 is a side plan view of the gravity valve of FIG. 8.

FIG. 10 is a perspective view of the gravity valve of FIG. 8.

DETAILED DESCRIPTION

To describe the present invention, reference will now be made to theaccompanying drawings. The present invention may be used with a bloodprocessing apparatus such as a SPECTRA OPTIA® blood component centrifugemanufactured by CaridianBCT, Inc, or a TRIMA® or TRIMA ACCEL® bloodcomponent centrifuge also manufactured by CaridianBCT, Inc. Theinvention may also be used with other blood component centrifuges. Theabove-named centrifuges incorporate a one-omega/two-omega seal-lesstubing connection as disclosed in U.S. Pat. No. 4,425,112 to provide acontinuous flow of blood to and from the rotor of an operatingcentrifuge without requiring a rotating seal.

An embodiment of the invention comprises an improved Ieuko-reduction orcell separation chamber for removal of white blood cells (“WBC”) orother selected types of cells such as mesenchymal stem cells from bloodcomponents. A related separation chamber is described incommonly-assigned U.S. application Ser. No. 12/209,793.

It is desirable for a separation chamber to separate greater than 99.99%of entrained WBC from platelet or plasma products obtained bycentrifugal apheresis, which is an extremely high value. The process forthis separation is based on the phenomenon of particle sedimentation ina fluid. The separated WBC consist of about 95% mononuclear cells (whichare about 90% leukocytes and 10% monocytes) and about 5% granulocytes.To accommodate the apheresis collection process, the separation chambermay function in an automatic mode as a continuous-feed process. Thisrequires an overflowing saturated bed of platelets above a bed ofmononuclear cells, which continuously accumulate during the collection.The saturated bed requirement operates in the dense-phase flow regime,which is characterized by high cell density. After a quantity or bolusof white blood cells are collected in the separation chamber, the WBCare removed from the chamber for collection. In devices withconventional separation chambers, this may be accomplished by reducingthe rotational speed of the centrifuge and increasing the flow rate ofplasma through the separation chamber, thus pushing the WBC bolus out ofthe outlet port. An additional line or tube, however, is connected to aside wall of the separation chamber through a side tap, near an inlet tothe chamber. The WBC are drawn out of the separation chamber through theside tap, which is “down hill” with respect to the gravitational fieldcreated by the centrifuge apparatus. There is little or no need tochange the speed of the centrifuge, nor is an increased inlet flow ofplasma needed to flush the collected WBC through the outlet. However,briefly pausing a pump in the collect line will pack WBC in theseparation chamber, allowing the cells to ultimately be removed from theseparation chamber in a smaller volume. A relatively small amount ofadditional plasma may be allowed to flow back into the chamber from theoutlet, or to flow in from the inlet to displace the WBC and fluid beingwithdrawn through the side tap. Preferably, the separation chamber isoriented such that the side tap is on the trailing side of theseparation chamber when the chamber is mounted on the rotor. That is, asthe rotor turns, the side tap is on the side of the separation chamberthat passes an observer last. A protruding inlet port may also beprovided coupled to the inlet of the separation chamber and adjacent theside tap outlet.

The protruding inlet port is a tube that transfers the entering flowpast a critical area where the wall of the chamber forms the apex of acone opening into the body of the chamber and past a side tap outlet forwithdrawing WBC from the chamber. The protruding port may eliminate aflow path along the wall that is caused by Coriolis acceleration.Coriolis acceleration pushes fluid entering the chamber towards theleading chamber wall. This entering fluid contains high concentrationsof WBC. If the fluid is pushed against the wall, rather than remaininggenerally in the center of the chamber, the fluid tends to flow up thewall, circumventing the bed of white blood cells and platelets thatcaptures WBC in the chamber by sedimentation forces. In addition, theprotruding inlet port blocks direct entry into the side tap outlet, thuscompelling the WBC to enter the area of the fluidized bed within theseparation chamber.

In the disclosed embodiment, a gravity valve selectively allows flowthrough a first flow path comprising a line fluidly coupled to theseparation chamber outlet and, alternatively, through a second flow pathcomprising a line fluidly coupled to the side tap outlet. The gravityvalve responds to the speed of the centrifuge rotor, on which the valveis mounted, to close or open the lines. No additional electricalconnection is needed to operate the valve, and the two lines areconjoined into a single line before the single line leaves the rotor.

A blood apheresis system 2 is schematically illustrated in FIG. 1.System 2 provides for a continuous blood component separation process.Generally, whole blood is withdrawn from a donor and is provided to ablood component separation device 6 where the blood is separated intovarious components and at least one of these blood components iscollected from the device 6. One or more of the separated bloodcomponents may be either collected for subsequent use or returned to thedonor. In the blood apheresis system 2, blood is withdrawn from thedonor and directed through a bag and tubing set 8, which includes anextracorporeal tubing circuit 10 and a blood processing vessel 12, whichtogether define a closed, sterile, disposable system. The set 8 isadapted to be mounted in the blood component separation device 6. Theseparation device 6 includes a pump/valve/sensor assembly 14, whichinterfaces with the extracorporeal tubing circuit 10, and a centrifugeassembly 16, which interfaces with the blood processing vessel 12.

The centrifuge assembly 16 may include a channel 18 in a rotatable rotorassembly 20, which rotor assembly provides the centrifugal forces(sometimes referred to as a “gravitational field”) required to separateblood into its various blood component types by centrifugation. Theblood processing vessel 12 may then be fitted within the channel 18.Blood can flow substantially continuously from the donor, through theextracorporeal tubing circuit 10, and into the rotating blood processingvessel 12. Within the blood processing vessel 12, blood may be separatedinto various blood component types and at least one of these bloodcomponent types (e.g., white blood cells, platelets, plasma, or redblood cells) may be removed from the blood processing vessel 12. Bloodcomponents that are not being retained for collection or for therapeutictreatment (e.g., platelets and/or plasma) are also removed from theblood processing vessel 12 and returned to the donor via theextracorporeal tubing circuit 10. Various alternative apheresis systems(not shown) may also be used, including batch processing systems(non-continuous inflow of whole blood and/or non-continuous outflow ofseparated blood components) or smaller scale batch or continuousRBC/plasma separation systems, whether or not blood components may bereturned to the donor.

Operation of the blood component separation device 6 is controlled byone or more processors included therein, and may advantageously comprisea plurality of embedded computer processors to accommodate interfacewith PC user facilities (e.g., CD ROM, modem, audio, networking andother capabilities). In order to assist the operator of the apheresissystem 2 with various aspects of its operation, the blood componentseparation device 6 includes a graphical interface 22 with aninteractive touch screen.

An extracorporeal tubing circuit 10, shown in FIG. 2, may include acassette 26 and a number of tubing/collection assemblies 28, 32, 34, 36,38 and 40. A blood removal-return tubing assembly 28 provides a needleinterface for withdrawing blood from a donor to the remainder of thetubing circuit 10 and for returning blood components and other fluids tothe donor. A single needle configuration is shown, but a double needleinterface may also be used. Three lines 42, 44, 46 are provided in bloodremoval-return tubing assembly 28 for blood removal, blood return, andanti-coagulent. A cassette 26 is connected between the tubing assembly28, which connects to the donor, and blood inlet/blood component tubingline sub-assembly 32, which provides the interface between cassette 26and blood processing vessel 12. The cassette 26 orients tubing segmentsin predetermined spaced relationships within the cassette 26 forultimate engagement with valve members on apheresis device 6. Suchvalves will, when activated, control flow through loops and tubing.

The tubing line sub-assembly 32 comprises four lines 60, 62, 64, and 66,shown in FIG. 2, for transport of blood and components to and from theprocessing vessel 12. The four lines are encased in a sheath 33 thatallows the one omega-two omega motion described in U.S. Pat. No.4,425,112. An anticoagulant tubing assembly 40, a vent bag 34, a plasmacollection assembly 36, and a white blood cell collection bag 38 arealso interconnected with cassette 26. Optionally, a red blood cellcollection assembly might also be provided through an auxiliary line 96,as is known in the art. The extracorporeal tubing circuit 10 and bloodprocessing vessel 12 are pre-connected to form a closed, sterilized,disposable assembly for a single use.

When the tubing circuit 10 has been mounted on the blood componentseparation device 6, saline solution (not shown) primes the tubingcircuit through a line 54 and filter 56 (see FIG. 2). Saline flowsthrough an internal passageway in the cassette 26 and through the line44 to the distal end of the blood removal assembly 28. Saline can thenflow up a blood withdrawal line 42 into the other tubes and passagewaysof the circuit 10 in preparation for blood processing. A supply or bag(not shown) of anticoagulant can then be connected to a distal end ofthe anticoagulant tubing assembly 40 in place of a saline supply.Anticoagulant solution flows past the filter 56 and a first pump loop 58through the anticoagulant line 44 to the distal end of the blood removalassembly. The pump loop 58 and other pump loops described herein couplewith peristaltic pumps on the blood processing device 6 in a knownmanner. The device 6 controls the direction and rate of flow of thefluids described herein by controlling the speed and direction of theperistaltic pumps and the position of various valves.

The blood removal line 42 conducts blood into the cassette 26, where theblood passes a first pressure sensor 80 and a second pump loop 82. Asecond pressure sensor 84, between second pump loop 82 with itsassociated pump and blood inflow line 60 to the blood processing vessel12, senses the fluid pressure effective at an inlet to the bloodprocessing vessel 12. Emanating from blood processing vessel 12 is anRBC outlet tubing line 62 of the blood inlet/blood component tubingassembly 32. The outlet tubing line 62 connects to an external loop 86to a return reservoir 88. The return reservoir 88 contacts sensors onthe device 6 that detect low and high fluid levels. The device 6 keepsthe fluid in the reservoir between these two levels by controlling flowout of the reservoir past a return pump loop 90 and a return pressuresensor 92. Because the fluid level in the reservoir 88 is constantlyrising and falling, a vent bag 34 connects to the reservoir 88 through avent tube 94. Air can flow between the reservoir 88 and the vent bag 34in a sterile manner. Fluid flows into a return tube 46 in the bloodremoval-return assembly 28. The removal-return assembly 28 alsocomprises the line 44 for adding priming solution (saline) oranti-coagulant solution, as described above. If desired, red blood cellscould be withdrawn through auxiliary line 96 and collected in acollection bag (not shown). Alternatively, a bag containing replacementfluid (not shown) may be connected to a spike or Luer connector 98 onthe auxiliary line 96, allowing replacement fluid to pass through thereturn loop 86 into the reservoir 88. Blood components and replacementfluid are then returned to the donor.

Equivalently, it is also known to couple the red blood cell line 62 to aperistaltic pump and to provide an automatic valve to select blood flowpaths, as shown, for instance in U.S. patent application Ser. No.12/959,987.

Plasma may also be collected from the blood processing vessel 12 intoplasma bag 36. When desired, plasma is withdrawn from the bloodprocessing vessel 12 through plasma line 66 to a pump loop 100. A valve101 diverts the plasma either into a collect tube 102 to the plasma bag36, or into connecting loop or line 104 to the reservoir 88. Excessplasma in the reservoir 88 is returned to the donor in the same way asred blood cells, as described above.

White blood cells and platelets flow out of the blood processing vessel12 through a cell line 68 into a cell separation chamber 114, which isfurther described below. The contents of the separation chamber flow outof the separation chamber either through a primary outlet line 64, 64′at a primary outlet 116 (See FIG. 5) or through a secondary outlet line65 at a secondary or side tap outlet 119 near the inlet 118 of theseparation chamber, as will be discussed below. The primary outlet line64 passes through the tubing line sub-assembly 32 and sheath 33 to thecassette 26. In the cassette 26, the fluid from the outlet line passes ared-green photo sensor 106, which may be used to control periodicflushing of white blood cells out of the cell separation chamber 114into the collect bag 38. The selected cells flow through a pump loop orline 108, which engages a peristaltic pump on the separation device 6.The pump loop 108 connects to a valved passageway in the cassette 26.The blood processing device 6 can control a valve 121 to direct whiteblood cells or other selected cells either into a collect tube 110 andthence into the collect bag 38, or into a connection loop or line 112and thence into the reservoir 88. Excess white blood cells in thereservoir 88 may be returned to the donor in the same way as red bloodcells and plasma, as described above. Alternatively, for mesenchymalstem cell (MNC) collection, wherein platelets are usually returned tothe donor, the MNC are withdrawn through the side tap outlet 119 intosecondary outlet line 65, to primary outlet line 64, past loop 108 andinto the collect tube 110 for storage in the collect bag 38.

During a blood removal, whole blood will be passed from a donor intotubing line 42 of blood removal tubing assembly 28. The blood is pumpedby the device 6 via pump loop 82, to the blood processing vessel 12, viathe cassette 26 and line 60 of the blood inlet/blood component tubingassembly 32. After separation processing in vessel 12, uncollected bloodcomponents are transferred from the processing vessel 12 to and throughcassette 26 and into reservoir 88 of cassette 26, which is filled up toa predetermined level. The blood component separation device 6 mayinitiate a blood return submode wherein components may be returned tothe donor through return line 46. The cycle between blood removal andblood return submodes will continue until a predetermined amount ofblood components have been harvested. In an alternative double needlescheme, as is known in the art, blood may be removed from the donor andreturned to a donor through two separate needles. See, for example, USPatent application 2010/160137.

A bracket 130 is provided on a top surface of the centrifuge assembly16. The bracket releasably holds the cell separation chamber 114 on thecentrifuge assembly 16 so that an outlet 116 of the cell separationchamber 114 is positioned closer to the axis of rotation than an inlet118 of the chamber 114. The bracket orients the chamber 114 on thecentrifuge assembly 16 with a longitudinal axis of the cell separationchamber 114 in a plane transverse to the rotor's axis of rotation. Inaddition, the bracket is arranged to hold the cell separation chamber114 on the centrifuge assembly 16 with the cell separation chamberoutlet 116 facing the axis of rotation. Although the chamber 114 ispreferably on a top surface of the centrifuge assembly 16, the chamber114 could also be secured to the centrifuge assembly 16 at alternatelocations, such as beneath the top surface of the centrifuge assembly16. In FIG. 6 and FIG. 7, the separation chamber 114 and outlet lines64, 64′ and 65 are shown, but the blood processing vessel 12 and theremaining lines connected thereto have been omitted for clarity ofillustration. As mentioned above, the blood processing vessel 12 wouldordinarily be inserted in the channel 18.

FIG. 3 schematically illustrates the blood processing vessel 12 and cellseparation chamber 114. The blood processing vessel 12 has a generallyannular flow path and includes an inlet portion 120 and an outletportion 122. The inflow tube 60 connects to the inlet portion 120 forconveying a fluid to be separated, such as whole blood, into the bloodprocessing vessel 12. During a separation procedure, substances enteringthe inlet portion 120 flow around the vessel 12 and stratify accordingto differences in density in response to rotation of the centrifugeassembly 16. The outlet portion 122 includes outlets for the RBC line62, the plasma line 66, and buffy coat or white blood cell line 68 forremoving separated substances from the blood processing vessel 12. Eachof the components separated in the vessel 12 is collected and removed inonly one area of the vessel 12, namely the outlet portion 122.

The outlet of the line 68 is connected to the cell separation chamberinlet 118 to pass intermediate density components, including white bloodcells or mesenchymal stem cells (MNC), into the cell separation chamber114. Components initially separated is in the blood processing vessel 12are further separated in the cell separation chamber 114. For example,white blood cells could be separated from plasma and platelets in thecell separation chamber 114. This further separation takes place byforming a saturated fluidized bed of particles in the cell separationchamber 114. Plasma and platelets would flow out of the cell separationchamber 114 while white blood cells were retained in the chamber.Similarly, granulocytes could be separated from red blood cells in likemanner.

As schematically shown in FIG. 3, a plurality of pumps 124, 126, and 128are provided for adding and removing substances to and from the bloodprocessing vessel 12 and cell separation chamber 114. An inflow pump 124is coupled to the inflow line 60 at pump loop 82 (FIG. 2) to supply thesubstance to be separated, such as whole blood, to the inlet portion120. In addition, a first collection pump 126 is coupled at loop 100 tothe plasma line 66. A second collection pump 128 is coupled to thecollection line 64 at loop 108. The second collection pump 128 drawsliquid and particles either from the cell separation chamber outlet 116or from the side tap outlet 119 and causes liquid and particles to enterthe cell separation chamber 114 via the cell separation chamber inlet118. In the disclosed embodiment, plasma and platelets are usuallywithdrawn from the outlet 116 of the cell separation chamber 114 throughline 64′. In the prior art, collected white blood cells or MNC or othercomponents would be flushed from the chamber 114 through the first cellcollection line 64 by either increasing the fluid flow through thechamber 114 or by slowing the rotor or both. In the disclosedembodiment, on the other hand, the secondary outlet line 65 connects tothe cell collection chamber 114 near the inlet 118 at the side tapconnection 119. A gravity valve 134 selectively closes the outlet lines64′, 65. The outlet lines 64′, 65 are joined into a common outlet line64, which also forms loop 108. Thus, the peristaltic pump 128, which iscoupled to loop 108, can draw fluid either from the outlet 116 or theside tap outlet 119, depending on the gravity valve 134.

During the formation of the fluidized bed of cells in the chamber 114,platelet rich plasma (PRP) or platelets would ordinarily be drawn fromthe outlet 116 through line 64′. During expression of collected cells(e.g., MNC), the collected cells would be drawn through the side tap 119and secondary outlet line 65. Since the collected cells would berelatively heavier than plasma, they would tend to fall towards the sidetap 119 and could more easily be withdrawn from the chamber 114. Beyondpump 128, loop 108 again divides into the two lines 110, 112. The valve121 on the device 6 selectively opens and closes the lines. Line 112 iscoupled to the reservoir 88 and ordinarily returns PRP to the donor.Line 110 is coupled to a collect bag 38 and allows the collected cellsto flow into the collect bag 38.

The first collection pump 126, which is coupled to loop 100, removesprimarily low-density substances such as plasma directly from the bloodprocessing vessel 12 via the plasma line 66. The plasma could either becollected in plasma bag 36 through line 102, or returned to the donorthrough connecting loop or line 104 and the reservoir 88. Valve 101selectively opens and closes the lines 102, 104 to direct the flow ofplasma either to the bag 36 or to the reservoir 88.

The pumps 124, 126, and 128 are peristaltic pumps, which preventsignificant damage to blood components. The pumps 124, 126, and 128control the flow rate of substances flowing to and from the bloodprocessing vessel 12 and the cell separation chamber 114. A saturatedfluidized bed of particles is maintained within the cell separationchamber 114 to cause other particles to be retained in the cellseparation chamber 114.

Blood within the processing vessel 12 is subjected to centrifugal forcecausing components of the blood components to separate. The componentsof whole blood stratify in order of decreasing density as follows: (1)red blood cells, (2) white blood cells, (3) platelets, and (4) plasma.The controller regulates the rotational speed of the centrifuge channelassembly 16 to ensure that this particle stratification takes place. Alayer of red blood cells (high density components) forms along the outerwall of the processing vessel 12 and a layer of plasma (lower densitycomponents) forms along the m inner wall of the processing vessel 12.Between these two layers, the intermediate density platelets and whiteblood cells (intermediate density components) form a buffy coat layer.Preferably, the separation is observed in two dimensions by a camera andcontrolled as described in U.S. Pat. No. 7,422,693, which isincorporated herein by reference.

The cell separation chamber is shown in detail in FIGS. 4 and 5. Thecell separation chamber 114 may be constructed in two pieces, a mainbody 200 and a cap 202, both being symmetrical around an axis 204. Themain body 200 has an inlet 118 comprising a through bore 206 and aconcentric stopped bore 208. The diameter of the through bore 206corresponds to the inside diameter of the cell line 68, while thediameter of the stopped bore 208 corresponds to the outside diameter ofthe line 68, so that the cell line 68 can be seated in the stopped bore208 and a fluid passageway of constant diameter can be formed betweenthe line 68 and the through bore 206. The through bore 206 opens into afrustro-conical segment 210. A wall 212 of the frustro-conical segment210 may comprise a plurality of steps 214 which generally taper awayfrom the axis 204. Straight or curved walls may also be used in thefrustro-conical segment 210, as shown in FIG. 6 and FIG. 7. The throughbore 206 rises into the frustro-conical segment 210 through a protrudinginlet 216. A mouth 218 of the protruding inlet 216 opens into thefrustro-conical segment 210 spaced away from the wall 212, therebyforming a circumferential well 220 between the wall and the protrudinginlet. A stream of fluid leaving the protruding inlet and entering thechamber is insulated from the effects of the wall 220 by a relativelystatic fluid layer. The stream is therefore less likely to adopt a flowpath along the wall, under the influence of Coriolis forces, but ratherwill remain in the center of the chamber, allowing more uniform mixingof cells and other particles within the chamber. An inner surface 219 ofthe protruding inlet flares slightly outwardly towards the mouth 218 ofthe protruding inlet 216. This reduces the flow velocity of fluidpassing through the protruding inlet and lessens Coriolis effects as thefluid enters the chamber.

In the illustrated embodiment, the main body 200 of the cell separationchamber 114 further comprises a circumferential flange 244, which issupported in the bracket 130. The cap 202 comprises a rim 246 that fitsagainst the flange 244. An interlocking groove and ridge (not shown) maybe provided between the rim 246 and flange 244 for sealing, if desired.In addition, a plurality of struts 245 may be provided as shown in FIG.6 and FIG. 7. The cap 202 and main body 200 may be joined by ultrasonicwelding or other suitable techniques as known in the art. The cap opensinto an abrupt frustro-conical segment 248. The abrupt segment 248tapers towards the axis 204. The abrupt segment 248 funnels bloodcomponents into the outlet 116 without excessive turbulence or damage tothe blood components. The outlet 116 comprises a through bore 250 and aconcentric stopped bore 252. The diameter of the through bore 250corresponds to the inside diameter of the outlet line 64′, while thediameter of the stopped bore 252 corresponds to the outside diameter ofthe cell line 64, so that the line 64′ can be seated in the stopped bore252 and a fluid passageway of constant diameter can be formed betweenthe line 64′ and the through bore 250. The through bore 250 opens intothe frustro-conical segment 248.

As described above, the separation chamber 114 further comprises a sidetap outlet 119. The outlet 119 also comprises a through bore 228 and aconcentric stopped bore 230. The diameter of the through bore 228corresponds to the inside diameter of the outlet line 65, while thediameter of the stopped bore 230 corresponds to the outside diameter ofthe outlet line 65, so that the line 65 can be seated in the stoppedbore 230 and a fluid passageway of constant diameter can be formedbetween the line 65 and the through bore 228. The primary outlet line64′ and the secondary outlet line 65 are fluidly connected at a coupling253, which allows fluid to pass from either line 64′, 65 into commonoutlet line 64.

In the separation chamber 114, an overflowing saturated bed of plateletsforms above a bed of mononuclear cells, which continuously accumulateduring the collection process. The saturated bed operates in adense-phase flow regime, which is characterized by high cell density.After a quantity or bolus of white blood cells or other selected cellsis collected in the separation chamber, the cells are removed from thechamber for collection. The selected cells are drawn out of theseparation chamber 114 through the side tap outlet 119, which is “downhill” with respect to the gravitational field created by the centrifugeapparatus. The speed of the centrifuge is only changed to operate thegravity valve 252, as explained below, and an increased inlet flow ofplasma is not needed to flush the collected cells through the outlet116. With the line 64′ closed and the line 65 open, the collected cellsare drawn out of the separation chamber for collection through the sidetap outlet 119. A relatively small amount of additional plasma may beallowed to flow back into the chamber 114 from the outlet 116, or toflow in from the inlet 118 to displace the cells and fluid beingwithdrawn through the side tap outlet 119.

The gravity valve 252 comprises a housing 254 mounted on the centrifugerotor 16 adjacent the bracket 130 for the separation chamber 114. Thehousing 254 supports a two-headed plunger 256 such that the plunger 256is aligned on a radial line from the axis of rotation of the centrifugerotor. The plunger 256 has an inward-facing head 258 and anoutward-facing head 260 mounted on opposite ends of a shaft 262. Theshaft 262 slides in a bushing 264 mounted on the housing 254. Acompression spring 266 mounted around the shaft 262 between the bushing264 and the inward-facing head 258, presses the head 258 towards aninner end wall 268 of the housing 254 and biases the plunger 256 towardsthe axis of rotation of the rotor. The outward-facing head 260 faces anouter end wall 270 of the housing 254. Line 65, which is in fluidcommunication with the side tap outlet 199, is placed between theoutward-facing head 260 and the outer end wall 270. A beam 272,symmetrically attached to the shaft 262 provides three functions. Thebeam 272 prevents the shaft and attached heads from rotating; itprovides a grip whereby an operator can move the inward-facing head 258away from the end wall 268, thereby allowing line 65′ to be placedbetween the head 258 and the end wall 268; and it provides increasedmass such that changing the rotational speed of the rotor 16 will movethe plunger 256 radially in and out.

Each of the heads 258, 260 comprises a cylindrical body 274 and a wedgeend 276. Each wedge end 276 has two planar faces 278, 280 that meet at avertical edge 282. The edges 282 allow the gravity valve 252 to pinchthe lines 64′, 65 against the adjacent end walls 268, 270. The gravityvalve also provides means for holding the lines 64′, 65 in a selectedposition between the end walls 268, 270 and the heads 258, 260. Theinner end wall 268 is adjacent two side walls or wings 284, 286. Slots288, 290 between the end wall 268 and the adjacent side walls 284, 286allow the primary outlet line 64′ to be inserted into aligned bores 292,294. The diameter of the bores 292, 294 is slightly larger than thewidth of the slots 288, 290 so that the elasticity of the line 64′allows the line 64′ to be forced through the slots 288, 290 and retainedin the aligned bores 292, 294. Similarly, the outer end wall 270 isadjacent two side walls or wings 296, 298. Slots 300, 302 between theend wall 270 and the adjacent side walls 296, 298 is allow the secondaryoutlet line 65 to be inserted into aligned bores 304, 306. Again, thediameter of the bores 304, 306 is slightly larger than the width of theslots 300, 302 so that the elasticity of the line 65 allows the line 65to be forced through the slots 300, 302 and retained in the alignedbores 304, 306.

In operation, when the rotor is spinning at relatively high speed, themass of the plunger 256 including the beam 272 moves the plunger 256outwardly in the gravitational field against the force of the spring266. This motion pinches the secondary outlet line 65 between theoutward-facing head 260 and the outer wall 270, thereby closing thesecondary outlet line 65 and opening the primary outlet line 64′. Thisallows selected cells to accumulate in the cell separation chamber 114.When sufficient cells are collected, the apparatus 6 slows the rotor 16.The spring 266 forces the plunger 256 inward toward the axis ofrotation. This motion closes the primary outlet line 64′, while openingthe secondary outlet line 65. The selected cells can be extractedthrough the side tap outlet 119 on the cell separation chamber 114.

Although the inventive device and method have been described in terms offiltering white blood cells, this description is not to be construed asa limitation on the scope of the invention. It will be apparent to thoseskilled in the art that various modifications and variations can be madeto the structure and methodology of the present invention withoutdeparting from the scope or spirit of the invention. Rather, theinvention is intended to cover modifications and variations providedthey come within the scope of the following claims and theirequivalents.

1. A blood cell collection system comprising a centrifuge rotor; a bloodprocessing chamber mounted on said rotor; a generally frustro-conicalcell separation chamber in fluid communication with said bloodprocessing chamber; the cell separation chamber having an inlet and aprimary outlet, said inlet being connected to said blood processingchamber, and a side tap outlet on said cell separation chamber, saidside tap outlet being adjacent said inlet, and a gravity valve mountedon said rotor, said gravity valve closing and opening said outlets inresponse to a selected speed of said rotor.
 2. The blood collectionsystem of claim 1 wherein said gravity valve comprises a radiallyoriented shaft slidingly mounted in said gravity valve.
 3. The bloodcollection system of claim 2 wherein said gravity valve furthercomprises a spring biasing said shaft towards an axis of rotation ofsaid rotor.
 4. The blood collection system of claim 3 wherein saidspring is mounted around said shaft.
 5. The blood collection system ofclaim 3 wherein said spring is a compression spring.
 6. The bloodcollection system of claim 2 wherein said gravity valve furthercomprises at least one first head mounted on an end of said shaft. 7.The blood collection system of claim 6 wherein said gravity valvefurther comprises a second head mounted on another end of said shaft. 8.The blood collection system of claim 6 further comprising at least onetube fluidly connected to at least one of said outlets of saidseparation chamber and wherein said gravity valve further comprises anend wall facing said head and means for securing said tube between saidhead and said end wall.
 9. The blood collection system of claim 7further comprising a first tube fluidly connected to said primary outletof said separation chamber, a second tube fluidly connected to said sidetap outlet of said separation chamber, and wherein said gravity valvefurther comprises a first end wall facing said first head and means forsecuring said first tube between said first head and said first endwall, and a second end wall facing said first head and means forsecuring said second tube between said second head and said second endwall.
 10. A blood cell collection system comprising a centrifuge rotor,and a gravity valve mounted on said rotor, said gravity valve adapted toclose and open in response to a selected speed of said rotor.
 11. Theblood collection system of claim 10 wherein said gravity valve comprisesa radially oriented shaft slidingly mounted in said gravity valve. 12.The blood collection system of claim 11 wherein said gravity valvefurther comprises a spring biasing said shaft towards an axis ofrotation of said rotor.
 13. The blood collection system of claim 12wherein said spring is mounted around said shaft.
 14. The bloodcollection system of claim 12 wherein said spring is a compressionspring.
 15. The blood collection system of claim 11 wherein said gravityvalve further comprises at least one first head mounted on an end ofsaid shaft.
 16. The blood collection system of claim 15 wherein saidgravity valve further comprises a second head mounted on another end ofsaid shaft.
 17. The blood collection system of claim 15 wherein saidgravity valve further comprises an end wall facing said head and meansfor securing a tube between said head and said end wall.
 18. The bloodcollection system of claim 16 further comprising a first end wall facingsaid first head and means for securing a first tube between said firsthead and said first end wall, and a second end wall facing said firsthead and means for securing a second tube between said second head andsaid second end wall.
 19. A disposable blood separation set comprising acircumferential blood processing chamber adapted to be mounted on acentrifuge rotor; an inlet line fluidly connected to said bloodprocessing chamber; a generally frustro-conical cell separation chamberin fluid communication with said blood processing chamber and adapted tobe mounted on said centrifuge rotor; the cell separation chamber havingan inlet and a primary outlet, said inlet being fluidly connected tosaid blood processing chamber, a side tap outlet on said cell separationchamber, said side tap outlet being adjacent said inlet, a first outletline fluidly coupled to said primary outlet, a second outlet linefluidly coupled to said side tap outlet, and a common outlet line, saidfirst and second outlet lines being fluidly coupled to said commonoutlet line adjacent said cell separation chamber at a junction, and asheath surrounding at least said inlet line and said outlet line,wherein said junction is between said cell separation chamber and saidsheath.
 20. The disposable blood separation set of claim 19 wherein saidinlet protrudes into said cell separation chamber.
 21. The disposableblood separation set according to claim 20 wherein said protruding inlethas a generally frustro-conical inner surface that slants radiallyoutwardly from said inlet to a mouth of said protruding inlet, saidmouth opening into said separation chamber.
 22. The disposable bloodseparation set of claim 20 wherein said cell separation chamber furthercomprises a circumferential well between said protruding inlet and saidinner wall and wherein said side tap outlet opens into said well. 23.The disposable blood separation set of claim 19 wherein each of saidcommon outlet line is fluidly connected to an extracorporeal tubingcircuit.